Propulsion of outboard engine driven boats or other marine craft



Nov. 20, 1962 DoWTY 3,064,616

G. H. PROPULSION OF OUTBOARD ENGINE DRIVEN BOATS OR OTHER MARINE CRAFTFiled March 25, 1960 it Stats This invention relates to the propulsionof boats or other marine craft hereinafter referred to for convenienceas boats. The invention is concerned with propulsion apparatus of thekind formed as an outboard unit suitable for mounting at the stern ofthe boat and including an engine driving a pump located in a duct todraw water from the duct entry which is arranged at just below the watersurface on which the boat lloats, and to expel water from the duct as ajet having a horizontal velocity com-v ponent the reaction of whichprovides the force to propel the boat. The jet nozzle may be locatedeither above or below the water surface. Such propulsion apparatus ishereinafter referred to as propulsion apparatus of the kind referred t0.

The present invention comprises a propulsion apparatus of the kindreferred to, per se, and in combination with a boat equipped with thesame, in which propulsion apparatus a plate, sheet or other member isarranged to provide a substantially rigid lower surface in contact withthe water on which the boat floats and extending rearwardly from thestern of the boat, the duct entry being accommodated by an apertureWithin this surface. The sheet, plate or other member may be anextension of or carried by the keel of the boat, or alternatively it maybe carried by the propulsion apparatus of the kind referred to. Thewidth of the sheet, plate or other member may be the same as the widthof the stern of the boat or it may be of such smaller width as toprovide a substantial area of surface around the duct entry. Preferablythe lower surface of the plate, sheet or other member is arranged to besubstantially continuous with the under surface of the keel of the boat.The duct entry may extend from a position closely adjacent to the end ofthe keel of the boat in a rearward and upward direction to facilitateentry of water into the duct when the boat is moving forwardly.

One example of the invention will be described with reference to theaccompanying drawings, in which:

FIGURE l is a vertical cross-sectional through the propulsion apparatusin position on the stern of a boat;

FGURE 2 is an end elevation of propulsion apparatus as shown in FlGUREl; and

FIGURE 3 is a plan view of the underside of the boat and propulsionapparatus.

in the drawings the stern 1 of the boat carries the outboard unit. Theoutboard unit is driven by a small internal combustion engine 2 fromwhich a drive shaft 3 extends vertically downwards. The drive shaft isconnected to drive an impeller 4 mounted within a pump casing S. Theimpeller is of the kind giving combined axial and centrifugal flow andthe output from the impeller d is collected within a volute 6 formedwithin the casing from which water is delivered to a jet pipe 7 which ishorizontally directed in the rearward direction. The g entry into thecasing 5 is formed by a comparatively large diameter tubular member Swhich extends downwardly from the impeller 4 and at its lower end formsthe entry 9 for water into the pump. T 1e tube 8, pump casing 5, volute6 and the jet nozzle 7 together form the duct through which water ispropeller by the impeller 4. At its lower end the tube S is integrallyformed with a flat ate plate 11 which in plan view is of D-shape, theflat side of the D being adjacent to the stern of the boat at the keel,all as is shown in FIGURE 3. The entry 9 is formed as an aperture withinthe plate 11, located closely adjacent to the end of the keel 12 of theboat whereby the entry tube 8 may extend rearwardly and upwardly fromthe entry 9 towards the impeller 21. In this way forward motion of theboat can be made to assist in the entry of water into the duct. Afairing 13 is formed around the entry tube S and supports the D-shapedplate 11 around its periphery on to the pump casing. The engine 2,volute 6, jet nozzle 7, pump casing 5, entry tube 8, fairing 13 andplate 11, in the form shown, are all rigidly secured together to formthe outboard unit which is detachably secured on the stern of the boatby means of mounting brackets 14 and 15 such that the unit while in usecannot move vertically relatively to the boat. The D-shaped plate 11,when the outboard unit is mounted in position, is in effect acontinuation of the keel 12 and a rubber sealing strip 16 may beprovided between plate 11 and the keel 12 to ensure that there is acontinuous smooth surface between the keel and the plate.

During operation as the boat is moving forwardly water enters the entry9 and is pumped by the impeller 4 through volute 6 to the jet tube 7from which it emerges as a horizontal jet the reaction of which propelsthe boat forwardly. A grill 17 may be provided over the entry 9 toprevent the entry of large pieces of solid matter into the pump. Smallpieces of solid matter which pass the grill are not sutiiciently largein size to cause any damage within the pump.

A deflector unit 18 is mounted on the jet nozzle 7 by means of a pair ofpivot pins 19 and 21 so as to be angularly movable about a substantiallyvertical axis relative to the jet nozzle 7, whereby the issuing jet maybe directed rearwardly or to port or starboard to produce a forwardimpulse, or one having an opposite lateral component. Controls, notshown, extend from the deiiecting unit 18 into the boat whereby thedeflector unit may be angularly adjusted for steering purposes by asteering control within the boat. A thrust reversing member 22 pivotallycarried within the deector unit 18 normally occupies the position shownin FIGURE l, but during reversal it may be moved upwardly about itspivot 23 to close the rearward end of the deector unit 18 and to open adownwardly and forwardly directed opening from detlector unit 18. Thewater issuing from the downwardly and forwardly directed opening isarranged to effect rearward propulsion of the boat, and during suchrearward propulsion as, indeed, during forward propulsion, movement ofthe deiiector 18 on pins 19 and 21 will steer the boat as desired.

Whilst the outboard unit has been shown rigidly attached to the stern ofthe boat with a deflector unit from the jet nozzle to effect steering itwould be appreciated that the outboard unit may equally well be mountedon the stern by brackets for pivotal movement as a whole about asubstantially vertical axis to effect steering. A pivotal coupling wouldthen be provided within the entry tube 8 to allow movement of theoutboard unit without moving the entry 9. Again alternatively theoutboard unit may be arranged for permanent attachment to the stern ofthe boat and the plate 11 may then form part of the structure of theboat itself. l

The advantage gained by the use of the invention lies in the fact thatthe plate 11 facilitates a smooth ow of water under the keel and aroundthe entry 9 into the duct, thus ensuring that there is a smooth ow ofnon-aerated water into the entry. lf the plate 11 were not providedwater passing from under the keel of the boat would be turbulent andaerated at the entry 9, resulting in less efficient propulsion.

The plate 11 may be adjustable relatively to the keel of the boat toensure that it occupies. the most useful position, but in use is fixedagainst vertical movement, at least, relative to the keel 12. Normally,its position will be that where the plate adjoins the keel to form asmooth continuation thereof. The adjustment may enable the plate 11 tobe moved up or down to an appropriate height and/or it may enable theplate to be moved angularly about a horizontal transverse axis. Suchangular adjustment may be conveniently attained by arranging bracket 15Yto be adjustable to and from the stern so that the outboard unit ineiect pivots about the lower bracket 12 and thus adjusts the angularsetting of the plate 11. The plate 11 may be of the full width of thekeel 12, or it may be somewhat narrower, as it is shown in FIGURE 3.

I claim as my invention:

l. in combination with a boat the keel whereof at its stern isrelatively liat, an outboard propulsion unit including means to mountthe same at the stern of the boat againstV relative vertical movement,said propulsion unit including a member formed with a bottom contoursimilar to that yof the boats keel at the stern, and located by saidmounting means with its bottom contour just below thesurtace of thewater on which the boat oats, and constituting in general a continuationof the keels contour, said member 'being formed with an aperture in itsbottom contour or" materially lesser area than the bottom contour perse, constituting an entry, said propulsion unit further including a ductleading from said entry to a rearwardly directed discharge nozzle, apump in said duct, and an engine driving said pump to draw water intothe entry and to eject it as a jet from the nozzle to propel the boat. p

2. A boat as claimed in claim l, wherein the said apertured member isxedly secured to the duct and is held in abutting relation with thestern of the boat.

3. Arboat as claimed in claim -l, wherein the rigid surface is less widethan the keel of the boat at the stern.y

4. An outboard propulsion unit including means for its securement to the,stern of va boat against relative vertical movement, said propulsionunit comprising a duct, an entry for the duct located, whe'nthepropulsion unit is so secured, just below the surface on which the boatfloats, a jet nozzle from the duct adapted to extend rearwardly from theboat, an enginja ypuinp located in the duct for drivingby the engine todraw water from the duct and to expel it as a jet from the nozzle, and amember xed to the duct providing a substantially rigid surface inContact with the water on which'the boat floats and adapted to extendrearwardly from the stern of the boat, to form substantially acontinuation of the boats keel, the said surt'ace having an apertureforming the duct entry.

5. The combination of YVaboat formedY with a keel 0f a given transversecontour, and a propulsion unit including a plate of a transverse contourcorresponding to that of the keel, and of a shape in plan to iit closelyto the boats stern, said plate having an aperture inset from at least(the side and rear edges of the plate, means supporting said plate fromthe boat against relative vertical movement, as a rearward continuationof said keel, to avoid cavitation in and consequentr aeration of thewater passing beyond the keel to the plate, and means to induct Waterthrough the plates aperture and to eject it with a horizontal component,for propulsion.

6. A boat as claimed in claim 5, including adjustment meansto'adjus'tthesetting of the Said member relatively to thekeel oftheiboat. t

7. A boat as claimed in claim 6, including a pair of vertically spacedbracketsv to secure the propulsion unit to the stern of the boatjtheupper' bracket'beingadjustable to vary the spacing of the upper part'ofthepropul'sion unit from'the stern to cause angular movement of thepropulsion unit and the said'm'ember.

References' Cited in the iile of this patent UNITED STATESV PATENTS1,498,919 Jensen .Tune 24, 1924' FOREIGNI PATENTS' 1,083,468 France June30, 1954

